Known devices for monitoring a moving yarn operate according to the capacitive or optical measuring principle. Depending on their measuring principle, such devices each have their preferred area of application and are geared quite specifically to such area of application.
U.S. Pat. No. 5,054,317 discloses a device for monitoring and/or measuring parameters of a continuous wire-like or fiber-like test material, in which both a capacitive measuring element and an optical measuring element are disposed in a measuring gap. The two measuring elements form two measuring zones which may overlap one another. This arrangement of multiple measuring elements in the same measuring gap calls for a mutual adaption of the two measuring systems, which leads to compromises and so does not allow the individual measuring systems to operate to optimum advantage.
Another perceived drawback in such known systems is that, depending on whether one or the other or even both measuring principles are to be used to monitor the yarn, a device specifically geared to the particular application has to be provided. For the manufacturer, this means that he has to develop and supply a plurality of designs, which therefore also entails an increased logistical outlay.